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attractor document in the cycling set of attractors. You should specify a
fairly long delay period for the nonattractor pages120 to 300 seconds or
moreso that the kiosk doesn't automatically reset while a user is read-
ing the current document. However, the delay period should be short
enough so that the kiosk resets to the attractor mode in a reasonable
period of time after the user finishes.
13.2.3. Pulling Non-HTML Content
The client-pull feature is not restricted to HTML documents, although it
is certainly easiest to create dynamic documents with HTML. With a bit
of server-side programming, you can add a
Refresh
field to the HTTP
header of any sort of document, from audio files to images to video
clips.
For example, create a real-time video feed by adding a
Refresh
header
field in each of a sequence of images grabbed and digitized from a cam-
era. Include a delay of 0 with the URL that points to the next image so
that as quickly as the browser displays one image, it retrieves the next.
Assuming that the network keeps up, the result is a crude (really crude)
TV.
Because the browser clears the window before presenting each subse-
quent image, the resulting flicker and flash make it almost impossible
to present a coherent sequence of images. This technique is more ef-
fective when presenting a series of images designed to be viewed as a
slide show, where the user expects some sort of display activity between
each image.
Perhaps a better use of the client-pull feature is with long-playing mul-
timedia documents, which the popular browsers use special helper ap-
plications to display. On a multitasking computer, such as one running
Linux or Windows, the browser downloads one document, while a helper
application plays another. Combine the client-pull capabilities with that
multitasking to improve multimedia document performance. Instead of
waiting for a single, large document such as a movie or audio file to
download before playing, break it into smaller segments, each auto-
matically downloaded by the previous segment via the
Refresh
header.
